Smoking articles such as cigarettes are conventionally made by wrapping a column of tobacco in a white wrapping paper. At one end, the smoking article usually includes a filter through which the article is smoked. Filters are attached to smoking articles using a tipping paper which is glued to the white wrapping paper. The wrapping papers and tipping papers used to construct smoking articles are typically made from flax or other cellulosic fibers and contain a filler, such as calcium carbonate.
Besides being used to hold the cigarette together, cigarette wrapping papers and tipping papers also contribute to and control many physical properties and characteristics of the cigarette. For instance, cigarette wrapping paper affects the rate at which the cigarette burns, the number of puffs per cigarette and the total tar delivery per puff. Another property of the cigarette that is affected by the wrapper is the appearance and characteristics of the ash that is formed as the cigarette burns. Ideally, cigarette ash should be cohesive, should not flake off from the cigarette, and should have an aesthetically pleasing appearance.
The quality of cigarette ash is generally determined by rating the ash according to four criteria. The first criteria is ash color. In general, a whiter ash has a more aesthetic appearance and is thus more desirable.
Another important characteristic of cigarette ash is its cohesiveness and its ability to avoid excessive flaking. The ash should not flake off the cigarette unless the cigarette is flicked or tapped on an object. Further, once the cigarette is tapped, the ash should break off in clumps and not disintegrate.
The last two criteria used to evaluate cigarette ash are dependent for the most part upon the cigarette wrapping paper and not upon the ash characteristics of the tobacco column. For example, cigarette ash is also evaluated by the thickness of the char line appearing on the wrapper as a cigarette is burned. Thinner char lines are preferred.
Finally, the last criteria is the extent to which the cigarette wrapper stains downstream (towards the filter) from the ash as the cigarette is smoked. A high quality wrapping paper will not stain or discolor throughout the length of the cigarette as the cigarette is puffed.
In the past, various methods have been devised in order to improve the ash characteristics of a smoking article. For instance, previous efforts for improving the appearance of ash have included changing the type of cellulosic fiber used to make the cigarette wrapping paper. Also, ash modifiers have been added to the paper or to the tobacco.
However, a need still remains for a method of improving cigarette ash characteristics without affecting the other properties of the cigarette. In particular, a need exists for a method that improves the ash characteristics of a cigarette wrapping paper without adversely affecting the permeability of the paper, or the taste, the burn rate, the puff count, or the tar delivery per puff of a cigarette incorporating the paper.